Electrode arrangement for direct current and furnace

ABSTRACT

A d.c. arc furnace for metallurgical purposes includes two or more electrodes arranged on the furnace vessel and projecting into the furnace vessel. To avoid actions of forces departing from the magnetic fields derived form the currents conducted to the electrodes and effecting deflections of the electric arcs, the electric supply means provided for each of the electrodes are each arranged in the immediate vicinity of the electrode to be supplied, the electric supply means of one electrode being arranged so as to be spacially separated from the electric supply means of the remaining electrodes, viewed in the peripheral direction of the furnace vessel.

BACKGROUND OF THE INVENTION

The invention relates to a d.c. arc furnace for metallurgical purposescomprising two or more electrodes arranged on the furnace vessel andprojecting into the furnace vessel.

A d.c. arc furnace of this type is known, for instance, from U.S. Pat.No. 3,949,151. That furnace comprises three electrodes arranged in aradially symmetrical manner, viewed in the ground section of thefurnace, wherein the electric supply means for feeding said electrodesare arranged to be concentrated on one side of the furnace. Each of theelectrodes is supplied with current by a separate rectifier, the highcurrent lines being conducted around the furnace to the respectiveelectrodes to be fed, departing from the rectifier stations arranged onone side of the furnace.

The high current lines are surrounded by strong electric fields inducingelectric-arc deflections of the electric arcs burning between theelectrode tips and the metal melt. This results not only in a stronglynon-uniform consumption of the electrodes, but also in a stronglythermal overload exerted on the brickwork of the furnace vessel. Toavoid such phenomena, six anodes are provided in the bottom of the d.c.arc furnace according to U.S. Pat. No. 3,949,151, which anodes areconnected with the electrodes projecting from top into the furnace via aseparate switch mechanism. That known electrode arrangement and itsspecial circuit is expensive in terms of construction and circuitry and,i.a., causes the furnace to function like an a.c. furnace.

SUMMARY OF THE INVENTION

The invention aims at avoiding these disadvantages and difficulties andhas as its object to avoid, in a d.c. arc furnace of the initiallydefined kind comprising several electrodes, electric arc deflectionsbrought about by the action of forces of the magnetic fields derivedfrom the currents conducted to the electrodes. The electric arcs are toburn uniformly throughout the total period of operation of a furnace andin a direction that can be exactly predetermined in order to avoidthermal asymmetry within the d.c. arc furnace and hence elevated wear ofthe brickwork of the furnace vessel.

In accordance with the invention, this object is achieved in that theelectric supply means provided for each of the electrodes are eacharranged in the immediate vicinity of the electrode to be supplied, theelectric supply means of one electrode being arranged so as to bespatially separated from the electric supply means of the remainingelectrodes, viewed in the peripheral direction of the furnace vessel.

The arrangement of the electric supply means, such as rectifierthrottles, etc., each in the immediate vicinity of the respectiveelectrode minimizes the unilateral asymmetrical mutual influence of theelectrodes the more so as in that case the high current lines directlylead to the supply means by a short way.

According to a preferred embodiment, the high current line conducted toone electrode--viewed in the ground section of the d.c. arc furnace--isarranged so as to extend in an approximately radial direction relativeto the vertical central axis of the furnace as far as to a rectifierstation associated with this electrode.

Preferably, the electrodes and the high current lines are arranged in anapproximately radially symmetrical manner. Thereby, unilateral forces ofthe magnetic fields acting asymmetrically on the electric arcs of theelectrodes may be completely avoided.

Suitably, each electrode is associated with a separate rectifierstation, which--viewed in the ground section of the d.c. arc furnace--iseach arranged in a region in the radial extension of the electrode.

To realize savings with the electric supply means, each electrode,according to a preferred embodiment, is associated with a separaterectifier station, at least two rectifier stations each being connectedto a common transformer station.

In the following, the invention will be explained in more detail by wayof an exemplary embodiment represented in the drawing, the drawingschematically illustrating a d.c. arc furnace in ground section.

BRIEF DESCRIPTION OF THE DRAWINGS

By 1 a furnace platform is denoted, in which a d.c. arc furnace 2 forthe production of steel is inserted. This electric arc furnace 2comprises a central charging shaft 4 vertically rising from the furnacelid 3 and reduced in its diameter relative to the diameter of thefurnace vessel 5.

DESCRIPTION OF A PREFERRED EMBODIMENT

The furnace vessel 5 comprises an oriel 6, which in a conventionalmanner is provided with a bottom tap, through which the melt can flowinto a ladle 7 placeable below the furnace vessel 5. A gas exhaust 8 isconnected to the charging shaft 4.

Four graphite electrodes 10, which are each supported on electrodecarrying means 11 by aid of which they are displaceable in the sense oftheir longitudinal axes and pivotable by a slight extent about theelectrode tips or about the center 12 of the furnace, preferably both inthe horizontal and in the vertical directions as indicated by the doublearrows 13, project into the furnace vessel 5 in a direction inclinedrelative to the horizontal plane from aside, i.e., through the verticalside wall 9 of the same. Each of these electrodes 10 is associated withits own rectifier station 14, with which the electrode 10 is eachconnected via a high current line 15 and which is each arranged in theimmediate vicinity of the electrode 10. Thus, it is feasible to connectthe electrodes 10 with the rectifier stations 14 by short high currentlines 15. The high current lines 15--viewed in ground section--eachextend approximately in the extension of the electrodes 10. Thisapplies, in particular, if the electrodes 10 are in the central positionof their pivoting range.

As is apparent from the drawing, both the electrodes 10 and the highcurrent lines 15--viewed in ground section--are arranged in a radiallysymmetrical manner. Slight deviations from the radially symmetricalarrangement of both the electrodes 10 and the high current lines 15 arepermissible, resulting from the mere fact that the electrodes arepivotable in the horizontal direction. For instance, the arrangement ofthe high current lines 15 in the hatched region 16 would have noconsiderable influence on the electric arcs of the neighboringelectrodes 10.

According to the exemplary embodiment represented in the drawing, eachof the rectifier stations 14 is associated with a separate transformerstation 17, both the rectifier stations 14 and the transformer stations17 being arranged below the furnace platform 1 and hence on a levelbelow the furnace vessel 5. Also a single transformer station 17 couldserve to supply two adjacently arranged rectifier stations 14.

The invention is not limited to the exemplary embodiment illustrated inthe drawing, but may be modified in various aspects. It is, forinstance, possible to equip the d.c. arc furnace 2 also with three, sixor eight electrodes 10. In such cases it is to be taken care that thehigh current lines 15--with the electrodes 10 arranged in a radiallysymmetrical manner--are conducted from the electrodes 10 to therespective rectifier stations 14 in an approximately radialdirection--likewise seen in ground section. The invention also may beapplied to d.c. arc furnaces comprising electrodes vertically projectingthrough the furnace lid 3.

We claim:
 1. A d.c. arc furnace for metallurgical purposes comprising afurnace vessel having a vertical axis, a periphery around the axis andthe periphery defining an interior of the vessel;at least two electrodesarranged on the furnace vessel and projecting into the interior of thefurnace vessel; a respective electric supply provided for each of theelectrodes, each supply comprising an electrical device and a highcurrent line from the device to the electrode, each electrical devicebeing arranged in the immediate vicinity of the respective electrode tobe supplied by the device through the respective high current line, theelectrical device for each electrode being arranged so as to bespatially separated from the electric devices of the electric suppliesfor the other electrodes around the periphery of the furnace vessel. 2.A d.c. arc furnace according to claim 1, wherein the high current lineconnected to each electrodes, viewed in a ground section of the d.c. arcfurnaces, extends in an approximately radial direction relative to thevertical axis of the furnace to the respective electric deviceassociated with the electrode.
 3. A d.c. arc furnace according to claim2, wherein the electrodes and the high current lines are arranged in anapproximately radially symmetrical manner.
 4. A d.c. arc furnaceaccording to claim 2, wherein each electrode is associated with andconnected by the respective high current line to a respective separateelectrical device and viewed in the ground section of the d.c. arcfurnace each device is arranged in a region that is a radial extensionof the respective electrode.
 5. A d.c. arc furnace according to claim 4,wherein each electrical device comprises a rectifier station for therespective electrode.
 6. A d.c. arc furnace according to claim 3,wherein each electrode is associated with and connected by therespective high current line to a respective separate electrical deviceand, viewed in the ground section of the d.c. arc furnace, eachelectrical device is arranged in a region that is a radial extension ofthe respective electrode.
 7. A d.c. arc furnace according to claim 6,wherein each electrode is associated with and connected by therespective high current line to the electrical device comprising aseparate respective rectifier station;a common transformer station forat least two of the rectifier stations for two of the electrodes.
 8. Ad.c. arc furnace according to claim 5, wherein each electrode isassociated with and connected by the respective high current line to aseparate respective rectifier station;a common transformer station forat least two of the rectifier stations for two of the electrodes.
 9. Ad.c. arc furnace according to claim 2, wherein each electrical devicecomprises a rectifier station for the respective electrode.
 10. A d.c.arc furnace according to claim 1, wherein each electrical devicecomprises a rectifier station for the respective electrode.